The thickness of the continental crust is ... The main features of the structure of the earth's crust

The continents were formed from the massifs of the earth's crust, which to some extent protrudes above the water level in the form of land. These blocks of the earth's crust have been split for a million years, shifted, parts of them crumpled to appear in the form that we know now.

Today we will consider the largest and smallest crustal thickness and features of its structure.

A little bit about our planet

At the beginning of the formation of our planet, multiple volcanoes operated here, constant collisions with comets occurred. Only after the bombing stopped, the red-hot surface of the planet froze.
That is, scientists believe that initially our planet was a barren desert without water and vegetation. Where did it take so much water - still remains a mystery. But not so long ago, large reserves of water were discovered underground, perhaps, they became the basis of our oceans.

Alas, all the hypotheses about the origin of our planet and its composition are more assumptions than facts. According to A. Wegener, originally the Earth was covered with a thin layer of granite, which in the Paleozoic era was transformed into ancestor Pangea. In the Mesozoic era Pangea began to split into parts, the continents formed gradually sailed from each other. The Pacific Ocean, says Wegener, is the remnant of the primary ocean, and the Atlantic and Indian are regarded as secondary.

Earth's crust

The composition of the earth's crust is almost the same as the composition of the planets of our solar system - Venus, Mars, etc. After all, the same substances served as the basis for all the planets of the solar system. And more recently, scientists believe that the collision of the Earth with another planet, called Thea, caused the fusion of two celestial bodies, and a splinter formed the Moon. This explains the fact that the mineral composition of the Moon is similar to the composition of our planet. Below we consider the structure of the Earth's crust - a map of its layers on land and ocean.

The crust is only 1% of the Earth's mass. Mainly it consists of silicon, iron, aluminum, oxygen, hydrogen, magnesium, calcium and sodium and another 78 elements. It is assumed that, in comparison with the mantle and core of the Earth's crust, the shell is thin and brittle, consisting mainly of light substances. Heavy substances, according to geologists, descend to the center of the planet, and the heaviest are concentrated in the core.

The structure of the earth's crust and a map of its layers are shown in the figure below.

Earth's crust

The Earth's crust has 3 layers, each with uneven layers covering the previous one. Most of its surface is the continental and oceanic plains. Continents also surround the shelf, which, after a snapping bend, turns into a continental slope (the area of the continental margin of the continent).
The Earth's crust is divided into layers:

1. Sedimentary.
2. Granite.
3. Basalt.

Sedimentary layer cover sedimentary, metamorphic and igneous rocks. The thickness of the continental crust is the smallest percentage.

Types of continental crust

Sedimentary rocks are clusters, among which are clay, carbonate, volcanogenic rocks and other solids. This is a kind of sediment that was formed as a result of certain natural conditions that used to exist on Earth. It allows researchers to draw conclusions about the history of our planet.

The granite layer consists of magmatic and metamorphic rocks, similar to granite in its properties. That is, not only granite makes up the second layer of the earth's crust, but these substances are very similar in composition and have approximately similar strength. The speed of its longitudinal waves reaches 5.5-6.5 km / s. It consists of granites, crystalline schists, gneisses, etc.

Basalt layer is composed of substances that are similar in composition to basalts. It is more dense than the granite layer. Under the basalt layer there is a viscous mantle of solid substances. Conditionally the mantle from the cortex is separated by the so-called Mohorovicic boundary, which, in fact, separates layers of different chemical composition. Characterized by a sharp increase in the speed of seismic waves.
That is, a relatively thin layer of the earth's crust is a fragile barrier that separates us from a red-hot mantle. The thickness of the mantle itself averages 3,000 km. Tantonic plates move along with the mantle, which, as part of the lithosphere, are a part of the earth's crust.

Below we consider the thickness of the continental crust. It is up to 35 km.

Power of the continental crust

The thickness of the earth's crust varies from 30 to 70 km. And if under the plains its layer is only 30-40 km, then under the mountain systems it reaches 70 km. Under the Himalayas, the thickness of the layer reaches 75 km.

The thickness of the continental crust is from 5 to 80 km and depends directly on its age. So, the cold ancient platforms (East European, Siberian, West Siberian) have a rather high power - 40-45 km.

In this case, each of the layers has its own thickness and thickness, which varies in different regions of the continent.

The thickness of the continental crust is:

1. Sedimentary layer - 10-15 km.

2. Granite layer - 5-15 km.

3. Basalt layer - 10-35 km.

Earth's crust temperature

The temperature rises as it deepens into it. It is believed that the core temperature is up to 5 000 C, but these figures remain conditional, since the species and its composition are still not clear to scientists. As it deepens into the earth's crust, its temperature rises every 100 m, but its figures vary depending on the composition of the elements and the depth. The oceanic crust has a higher temperature.

Oceanic crust

Initially, according to the scientists' assumptions, the Earth was covered by the oceanic layer of the crust, which differs somewhat in thickness and composition from the continental layer. The oceanic crust, probably, originated from the upper differentiated layer of the mantle, that is, in composition it is very close to it. The thickness of the oceanic crust is 5 times less than that of the continental type. However, its composition in the deep and shallow areas of the seas and oceans differs little from each other.

Layers of the continental crust

The thickness of the oceanic crust is:

1. A layer of oceanic water, the thickness of which is 4 km.

2. A layer of loose precipitation. The power is 0,7 km.

3. A layer composed of basalts with carbonate and rocky rocks. The average power is 1.7 km. It does not stand out sharply and is characterized by the compaction of the sedimentary layer. This variant of its structure is called suboceanic.

4. Basalt layer, not different from the continental crust. The thickness of the oceanic crust in this layer is 4.2 km.

The basalt layer of the oceanic crust in subduction zones (a zone in which one layer of bark absorbs the other) is converted into eclogites. Their density is so high that they sink deeper into the crust to a depth of more than 600 km, and then descend into the lower mantle.

Given that the lowest thickness of the earth's crust is observed under the oceans and is only 5-10 km, scientists have long been baptizing the idea of drilling bark at the depths of the oceans, which would allow a more detailed study of the internal structure of the Earth. However, the layer of the oceanic crust is very strong, and studies at the depth of the ocean make this task even more difficult.

Conclusion

The earth's crust, perhaps, is the only layer that has been thoroughly studied by mankind. But what is under it, still worries geologists. It remains only to hope that once unknown depths of our Earth will be studied.